I think from reading that a while ago, he made that himself, its one unit, the side panel wraps up and around the back, aux fuel tank. There was a guy on here who had a small hobby/company, retro raid I think it was called, who made O\S tanks and aux tanks, but last I heard they had ceased trading as it was starting to take up all their spare time. I f you can find anyone else making tanks, main or aux shout about it on here, I have not heard of any being made for quite a while.

Thanks Jibber.
In my trawl of the internet of seen quite a few in the same style. I thought there must be a manufacturer somewhere. Failing that I have a couple of mates who could fab up alloy tanks, at a price Got to find a VJ first.
Another one here:http://www.rallye-tenere.net/Umbauten.html

I'm not sure if you are chasing a rear tank for purely functional purposes, or for that genuine look. If its the former Nomda tanks made in Australia may be a decent option to consider... they have always been on my favourites list for if/when I set up a bike for longer tripshttps://www.nomadtanks.com.au/our-tanks/